I have installed "behind the grille" LED strip lights and determined I am going to tap off the driver's side factory fog lamp (now LED). What is the best path to get the 18awg wire into the engine compartment for the switch ON THE DRIVER's SIDE that will be installed under the dash? Look forward to hearing anyone's advice.

The picture below shows the lighting effect using an outside power source. You can see the wires hanging off the driver's side headlight. This is the connection side.

 

If I remember correctly, there is room in the side of the main wire harness grommet to poke a wire through on the drivers side. This is where I would fish through the tach and hood pin wires when I used to be an automotive electronics installer. I used a fish I made that was basically a large sewing needle about 8" long. It worked great to draw wires through soft rubber grommets in the firewall without making new holes and maintaining a weather seal.

 

Run the wire along the core support. Follow the headlight harness into the engine compartment, along the DS fender and through the firewall by the Ebrake cable. Drill a hole install a gromet for the they wire.